The present invention relates to certain novel di- and tetra-fluoro analogs of squalene which are useful as inhibitors of squalene epoxidase and as agents which lower total serum cholesterol in patients in need thereof. The present invention also provides pharmaceutical compositions for the use of these novel compounds as well as a novel process for their synthesis.
The conversion of the acyclic polyolefin squalene to the cyclic steroid lanosterol is a key step in the biogenesis of cholesterol. This conversion occurs in two steps. Squalene epoxidase catalyzes the conversion of squalene to (3S)-2,3-oxidosqualene. Oxidosqualene cyclase then converts (3S)-2,3-oxidosqualene to lanosterol. Lanosterol is converted through a number of subsequent enzymatic steps to cholesterol. Inhibition of squalene epoxidase decreases the amount of oxidosqualene available for conversion to cholesterol. Inhibition of squalene epoxidase thus results in a decrease in the amount of cholesterol synthesized and ultimately causes a lowering of cholesterol in the blood.
Sen and Prestwich [J. Med. Chem. 1989, 32, 2152-2158] have synthesized a variety of squalene analogs in an attempt to produce an effective inhibitor of squalene epoxidase.
Included in the compounds synthesized and tested for squalene epoxidase activity were the 1,1-di- and 1,1,22,22-tetra-bromo- and 1,1-di- and 1,1,22,22-tetra-chloro analogs of squalene. These compounds, unlike the di- and tetra-fluoro analogs of the present invention, were found to have no or very poor inhibitory effect on squalene epoxidase. Surprisingly, the di- and tetra-fluoro analogs of the present invention are very effective inhibitors of squalene epoxidase.
Atherosclerosis as manifested in its major clinical complication, ischaemic heart disease, continues to be a major cause of death in industrialized countries. It is now well accepted that atherosclerosis can begin with local injury to the arterial endothelium followed by proliferation of arterial smooth muscle cells from the medial layer to the intimal layer along with deposition of lipid and accumulation of foam cells in the lesion. As the atherosclerotic plaque develops it progressively occludes more and more of the affected blood vessel and can eventually lead to ischaemia or infarction. Therefore, it is desirable to provide methods of inhibiting the progression of atherosclerosis in patients in need thereof.
There is now a large body of evidence demonstrating that hypercholesterolemia is an important risk factor associated with heart disease. For example, in December 1984, a National Institute of Health Consensus Development Conference Panel concluded that lowering definitely elevated blood cholesterol levels (specifically blood levels of low-density lipoprotein cholesterol) will reduce the risk of heart attacks due to coronary heart disease. Accordingly, it is desirable to provide a method for reducing blood cholesterol in patients with hypercholesterolemia.
Typically, cholesterol is carried in the blood of warm-blooded animals in certain lipid-protein complexes such as chylomicrons, very low density lipoprotein (VLDL), low density lipoprotein (LDL), and high density lipoprotein (HDL). It is widely accepted that LDL functions in a way that directly results in deposition of the LDL cholesterol in the blood-vessel wall and that HDL functions in a way that results in the HDL picking up cholesterol from the vessel wall and transporting it to the liver where it is metabolized [Brown and Goldstein, Ann. Rev. Biochem. 52, 223 (1983); Miller, Ann. Rev. Med. 31, 97 (1980)]. For example, in various epidemiologic studies the LDL cholesterol levels correlate well with the risk of coronary heart disease whereas the HDL cholesterol levels are inversely associated with coronary heart disease [Patton et al., Clin. Chem. 29, 1890 (1983)]. It is generally accepted by those skilled in the art that reduction of abnormally high LDL cholesterol levels is effective therapy not only in the treatment of hypercholesterolemia but also in the treatment of atherosclerosis.
The novel di- and tertra-fluoro squalene analogs of the present invention are inhibitors of squalene epoxidase. These compounds are thus useful in lowering blood cholesterol in patients in need thereof.